Dr. O'Neil completed his orthopedic surgery residency training at Thomas Jefferson University Hospital in Philadelphia, Pennsylvania. Prior to residency, he completed undergraduate education at the University of Notre Dame and medical school at Thomas Jefferson University. He was born and raised in the Philadelphia area.

Dr. O'Neil is currently an orthopedic foot and ankle surgery fellow at Union Memorial Hospital in Baltimore, Maryland.

His research interests include total ankle arthroplasty; the diagnosis, treatment, and prevention of periprosthetic joint infection in the ankle; as well as helping to combat the opioid epidemic in the United States by better understanding patterns of prescribing and use following common orthopedic surgical procedures.